The [[[Smoothie]]] project will use the [[http://​www.allegromicro.com/​en/​Products/​Part_Numbers/​4983/​4983.pdf|Allegro A4983]] chip to drive the stepper motors.

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The [[Smoothie]] project will use the [[http://​www.allegromicro.com/​en/​Products/​Part_Numbers/​4983/​4983.pdf|Allegro A4983]] chip to drive the stepper motors.

It's a very nice chip, it has 1/16 microstepping,​ can drive up to 2A, and has the simple step/​direction interface.

It's a very nice chip, it has 1/16 microstepping,​ can drive up to 2A, and has the simple step/​direction interface.

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Most common way to use it is via the [[http://​www.pololu.com/​catalog/​product/​1201|Pololu Driver Carrier]], but in the case of [[[Smoothie]]], we want all of the 4 drivers directly on the PCB, so that they can share the heatsink/​fan,​ and also share some components.

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Most common way to use it is via the [[http://​www.pololu.com/​catalog/​product/​1201|Pololu Driver Carrier]], but in the case of [[Smoothie]],​ we want all of the 4 drivers directly on the PCB, so that they can share the heatsink/​fan,​ and also share some components.

Before designing the Smoothie PCB, it's important to be sure how exactly the A4983 works.

Before designing the Smoothie PCB, it's important to be sure how exactly the A4983 works.

Line 29:

Line 29:

A few notes :

A few notes :

* The dir pin is connected to +5V so it only goes one way, that's just because this is a test, just connect it to an arduino digital output, and you can change directions.

* The dir pin is connected to +5V so it only goes one way, that's just because this is a test, just connect it to an arduino digital output, and you can change directions.

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* 3 resistors are missing, if compared to the example in the datasheet. That's because as [[[Smoothie]]] will be USB-powered,​ we assume the power supply can be trusted. It reduces cost, and gives more free space around the chips ( there need to be no other component around the 4 A4983 so that they can be directly ​ in contact with the heatsink.

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* 3 resistors are missing, if compared to the example in the datasheet. That's because as [[Smoothie]] will be USB-powered,​ we assume the power supply can be trusted. It reduces cost, and gives more free space around the chips ( there need to be no other component around the 4 A4983 so that they can be directly ​ in contact with the heatsink.

That's all for today.

That's all for today.

Next step : controlling the current setting of the A4983 with the MCP4331 digital potentiometer.

Next step : controlling the current setting of the A4983 with the MCP4331 digital potentiometer.